Dalvik is a virtual machine used by Android. This is usually considered a Java virtual machine, although it is not quite correct. It uses an object model that is identical to Java, and its memory model is also almost equivalent. But dalvik VM is a register-based virtual machine, unlike Java virtual machines that are stack-based.
Accordingly, it uses a completely different bytecode than Java. However, the Android SDK includes a dx tool to translate Java bytecode into dalvik bytecode, so you can write Android applications in Java.